1. Field of the Invention
The present invention relates to telephony. More specifically, the present invention relates to integrated cordless and wireless telephones having a landline interface.
2. Description of the Related Art
Cordless telephones are similar to conventional corded telephones in that they are connected by wire to a local central office. However, they differ in that there is no cord between the base unit of the cordless telephone and the handset; thus, they are termed ‘cordless’ telephones. Cordless telephones add the convenience of mobility within the range of coverage of radio transceivers in the cordless telephone base unit and handset.
The deployment of cellular service established the beginning of a wireless telephony era. The first widely adopted and implemented standard in the United States was AMPS cellular. Later, other standards were implemented, including TDMA (IS-136), CDMA (IS-95), GSM, PCS (various standards), and others. All of the wireless telephones developed according to these standards share the characteristic that there is no local metallic loop employed to render service. Rather, a wireless telephone network is deployed by a service provider, and wide area coverage (at least respecting the coverage of a cordless telephone) is delivered via radio signals from a plurality of radio cell cites. The wireless telephones do not typically comprise a base unit; rather, the entire telephone circuitry is contained inside a single enclosure, including a battery.
Wireless telephones do suffer from certain disadvantages. They are physically small, and hence the user interface is rather compact, which somewhat reduces the convenience of operation. The transmitter power is controlled and kept low to conserve battery power. And, received signal strengths are low, due to frequency reuse plans and other network infrastructure considerations. This means that radio signal strength is often time so limited that interference and noise are prevalent and common annoyances during communications. The mobility of the wireless transceiver exacerbates the interference and noise problems because of the vagaries of radio propagation, including multi-path interference, Rayleigh fading, and physical blocking of radio signal paths. In addition, wireless telephones have limited battery life, especially during extended conversation times.
Cordless telephones offer improved user interfaces and performance over wireless telephones in most circumstances. Cordless telephones are usually larger and have more complete and convenient user interfaces. Cordless base units often times house voice messaging systems and/or speakerphones. Cordless telephones operate in small geographic areas so that signal levels at the receivers of both the base unit and handset are high, offering better receiver quieting, higher signal to noise ratios, and less interference and noise generally. They also offer longer battery life during both standby and talk times, owing to their larger batteries and their more extended times at rest on a charging cradle.
With the advent of the wireless era, the trend is toward using the wireless telephone as a principal telephone resource, even as compared to the traditional wired and corded telephones, which are coupled to the telephone network through a landline metallic conductor pair interfaced to a local central office. Users merely keep their wireless telephone with them at all times, whether during travel, at home, or at work. Thus, they are readily reachable by calling the wireless telephone number. However, this means that the aforementioned limitations of wireless telephones are always present for such users. It is known in the art to overcome these limitations by integrating a cordless base unit and handset with a wireless telephone interface such that the wireless telephone can act as the telephone service resource to the cordless telephone. Such a systems is described in a co-pending U.S. patent application filed on Dec. 13, 2000, assigned U.S. Patent Office Ser. No. 09/737,289, entitled CORDLESS AND WIRELESS TELEPHONE DOCKING STATION, invented by Uchiyama, who is the inventor of the present application. This approach provides the advantages of the cordless telephone device while utilizing a telephone resource accessed through a wireless telephone network. Such a device is referred to as a cordless and wireless telephone docking station.
A limitation exists in the utilization of the cordless and wireless docking station in that while the wireless telephone is removed from the docking station, the cordless portion that remains is not usable because there is no telephone resource available in the absence of the wireless telephone. Yet, many homes and offices have access to both wireless and landline telephone resources. This means that users of the cordless and wireless docking station require the use of two telephone terminal devices, one coupled to the landline services and the other coupled to the wireless telephone resource in order to access both telephone service resources.
Thus, there is a need in the art for an apparatus to consolidate landline and wireless telephone resources into a single device having cordless capability.